Rate of turn instrument



July 13, 1954 C. T. MORROW ETAL RATE OF TURN INSTRUMENT Filed July ll, 1950 3 Sheets-Sheet l No REFERENCE EMPL/FISI? POWER Sl/PFL Y July 13, 1954 Filed July 11, 1950 C. T. MORROW- ETAL RATE OF TURN INSTRUMENT 3 Sheecs-Sheel 2 INVENTORS July 13, 1954 c. T. MoRRow ET A1. 2,683,596

RATE OF' TURN INSTRUMENT Filed July ll, 1950 5 Sheets-Sheet 3 72 33 76 :il v n af 82 7a 7 75 Sp 77 Patented July 13, 1954 RATE OF TURN INSTRUMENT Charles T. Morrow, Great Neck, Roland E. Barnaby, Hicksville, and Lloyd A. Nevala, Lake Ronkonkoma, N. Y., assgnors to The Sperry Corporation, a corporation of Delaware Application July 11, 1950, Serial No. 173,112

18 Claims.

The present invention relates to apparatus for indicating and measuring the angular rate of change of orientation oi a body to which it is fixed, and is particularly adaptable for indicating and measuring the angular rate and direction oi change ci orientation of a movable craft.

The invention relates generally to the class of apparatus described in U. S. application Serial No. 622,739, filed October 17, 1945 in the name of Joseph Lyman, now Patent No. 2,513,340, wherein is disclosed an electrically oscillated tuning fork connected by a torsional constraining spring to a base adapted to be mounted on a craft whose rate of rotation or rate of change of orientation is to be measured, and in which pick-off means are provided for producing an electrical signal corresponding to the magnitude and direction of alternating torsional displacement between the tuning fork and the base or craft upon which the apparatus is mounted.

The present invention is directed specifically to the structural characteristics of such an apparatus and has for its principal object to provide apparatus characterized by extreme ruggedness, low noise level, fast response time, and good longterm stability for measuring the rate of change of orientation of a craft.

Another object of the present invention is to provide a rate of turn indicatingr and measuring apparatus of the above character in which spurious vibrations of the fork assembly parallel to the turn axis are reduced substantially to zero.

Another object is to provide an apparatus of the above character wherein spurious, reed-like, lateral or translational vibrations of the tuning fork assembly caused by mass unbalance of the tines or vibrations produced therein from some external source are greatly reduced or substantially eliminated.

Still another object of the present invention is to provide an apparatus of the above character in which the tine drive assembly may be adjusted to cause the tines to be vibrated or driven in a plane substantially coincident with the natural plane of vibration of the tines.

A further object of the present invention is to provide apparatus of the above character in which the torsion pick-orf devices may be adjusted so as to eliminate sensitivity to some spurious vibrations generated by mass unbalance, coercion in the drive means, and external vibrations.

A still further object of the present invention is to provide apparatus in which the torsional vibrations generated by turning movements of the craft on which it is mounted are damped or quickly suppressed upon completion of the said turning movements.

Other objects and features of the present invention will become apparent in the following detailed description thereof when read in the light of the accompanying drawings in which I have illustrated a preferred embodiment of the present invention, and in which:

Fig. 1 is a schematic perspective view oi the apparatus of my invention partially broken away to show the internal elements thereof;

Fig. 2 is a vertical section of the apparatus taken along a plane coincident with the normal plane of vibration of the tines;

Fig. 3 is a vertical sectional view of the apparatus taken in a plane at right angles to the normal plane of vibration of the tines;

Fig. 4 is a plan view, partially in section, taken along the line of 4 4 of Fig. 2;

Fig. 5 is a sectional view taken along the line 5 5 of Fig. 3;

Fig. 6 is a sectional view of a portion of the apparatus taken along line 6 5 of Fig. 4;

Fig. '.7 is a View partially in section of another portion of the apparatus taken along the line 'I 'l 0f Fig. 5; and

Fig. 8 is a schematic View showing the ends of the tuning fork of the apparatus in three conditions of mass unbalance.

Referring now to Fig. 1, the apparatus consists generally of a tuning fork element I l having substantially massive tines l and l5 mounted so that the tines will normally vibrate in a plane deiined by the axes XX', YY. The heel portion i6 of the fork is rigidly secured to the top of an intermediate portion or torsion structure il at the bottom ci which is secured, or formed integrally therewith, a relatively thin cylindrical torsion spring i8, which, in turn, is secured rigidly to a base I9 mounted on a craft or body, the rate of turn of which is to be measured. The torsion structure l'l is preferably constructed of non magnetic material for the purpose of minimizing stray ield coupling between the tine drive eld and the torsion pickup. Adjacent the top or open ends of tines I4 and l5 is a driving means which in the embodiment illustrated may take the form of electromagnetic drive coils 20, 2| adjustably secured to the sidewalls 22 of the apparatus (see Fig. 2). Between the open ends of tines I4 and E5, there is provided a vibration pickup device 23 which may be of the variable capacitance type. Drive coils 2G and 2i are connected in series and receive their driving energy from the output of a drive and reference arnpler 2S. One input of amplifier is connected with a power supply unit the other input is connected with capacity pickup 23. The pickup 2 excites the arnplirler so that the whole system, fork and arnplie is self-resonant at a frequency preferably corresponding to the natural frequency of vibretion or tuning fori; ii. The output of the drive a plifier be limited so that the amplitude of the drive voltage will not build up to destructive values.

es explained in the above-mentioned Lyman patent, as the tines ill and i5 are rapidly vibrated in the plane delinea by the axes XX', YY', and base ie is rotated about the YY anis, tuning fori; i can preserve angular momentum only by executing a. torsional vibration .about the YY axis proportional to the rate of tne 'turnii g movement of base le. The magnitude and pbase of this torsional vibration are expressed electrical ly by torsion 'pick-offs, generally indicated at and and are a measure of the magnitude direction, respectively, of the rate or" turn or" base is or craft on which the base mounted. The signal from the pick-offs in the illustrated einbodiinent of the present invention is supplied to one input of rate signal amplifier Bl, also connected with power supply unit 25. rlhe output or rate signal amplifier 3l is applied to a phase* sensitive detector 3S in which it is compared with the reference signal from the dive reference arnpliier 365 to thereby obtain a resul-.tant signal or phase and magnitude proportional to the rate of turn of the base member iii. This resultant signal may be connected to a suitable indicating device or rneter 3S calibrated to represent a measure ci the rate of turn of base is, rEhe embodiment of the presen'r invention herein illustrated is primarily suited to teleinetering applications. However, it should noted that in some applications of the invention, it may be desirable to use the output sigm nais from t'ne rate signal amplier to actuate an induction motor, a phase detector, or other converting device in some portion ci the system in which the apparatus is applied.

ln accordance with the present invention we have provided an apparatus responsive to turning movements of a base or craft upon which the apparatus is mounted which has extreme ruggedness and long-terni stability. For perfect stai. e., no drift in the absence or turning movements, it is theoretically suiicient to onal supports of the tuning fork cornpletely ree from all vibration at forli frequency except that due to rate of turn. In practice,

however, it is extremely difficult, if not impossible, to isolate the tuning fors: supports completely from all undesired vibrations. However, in the apparatus of the present invention, we have ren duced these undesired spurious vibrations to an absolute minimum and we have provided nie-ans for compensating for the eiiect of such spurious ibrations in the iinal rate or turn signal thered by providing a rate of turn detecting and Ineasurm ing apparatus having an exceptionally low drift rate.

In apparatus of this character one of the major causes of spurious or undesired vibrations arises from inass unbalance in the vibrating tuning i'orir tines. These undesired vibrations nay produce directly or indirectly spurious torsional vibrations about the sensitive axis or axis of symmetry YY. rlhe primary spurious vibrations caused by mass unbalance in the tines may be summarized as unbalance in the tines coincident with tne XX', YY', but to the inside or outside or tine axes C', as illustrated, which are transmitted to the output pick-cris and by ine-- chanical stresses within the iinite coi. tween the tuning iork and its support. We nave minimized or reduced substantially to aero this axial vibration by removing a calcclated amount of metal from the fork as carefully possible at the points illustrated in Fig. 3C, the mechanical construction described below. Since it is impossible to support the on tuning loris. a point which would in fact be nodal, we have reduced the size of the coupling to a minimum. However, Vibration of 'the tines it and `f produces stresses at the heel l5 or" the tuning foi stresses are transmitted through the finite connection or nodal coupling between is and the top of torsion structure il, as by the double ended arrows in Fig. 2. el," stresses will be produced torsion structure in the plane at right angles to that oi the abo ementioned stresses. These stresses are cated by the double ended arrows in 3 or the drawings. Both of these stresses, if .not eliminated or greatly reduced, may cause errors in the output signal because of possible coupling into torsional vibrations which, like the efiect or' a rate of turn, can generate signals in the torsion pick-offs. We have elirni er reduced substantially to zero these axial vibrations providing two pairs of slots it and il cut in the torsion structure il in horizontal planes one above the other. These slots extend ir ""-rdiy from opposite sides of the tors on stru e and form two substantially narrow, elongated connecting webs fili and il in toi strucJ il. These webs extend diametricaiiy me torsion structure il at right angles to each in the planes respectively defined ZZ', YY and EGT, YY.' Nebs il and f vide isolating means icr substantially p ing the above-described spurious vi` from reaching the torsion spring a the pick-oils 36 and 3i.

The parallel rocking or anslational vibration in the plane XX', YY i y be caused by either the mass unbalance of g. 8.5i or 'by vibrations external ci the apparatu This lateral and rocking vibration may i cause of the reed-like cliaracterisu il and torsion structure othe ii and torsion structure il together like a reed, that is, a vibratory secured at one end and unrestrained the other, having a node in the region oi torsion spring In accordance with the present invention e have eliminated or greatly reduced these reefle vibrations by carefully removing material or mass from the tines at the points illustrated Fig. 8C and finally by providing lateral or anti-rocking supports generally indicated at and These supports eiectively control the lateral rocking resonances by tuning them to frequencies greatly spaced both from low frequency craft vibrations and from the natural resonance of fork II so that they will not affect the rate of turn signal at torsion pick-offs 3d and 3I. These lateral supports are positioned along the length of the apparatus preferably at the anti-nodal positions of the above-described reed-like vibrations. The upper lateral support 43 comprises a cartwheel-like structure having a rim 45 secured to the rigid housing sidewalls 22 for the apparatus. A plurality of spokes or strut-like elements 4e, 41 are fixed to a hub i8 and extend outwardly therefrom and are secured in rim 45. Hub 48 is secured to the top of torsion structure II as close as possible to axis YY.

It will be noted that the upper lateral support is located at a position above the tuning fork heel and is so constructed that it will not touch or aiect the heel portion I6 of the tuning fork II. This is accomplished by providing a pair oi prongs I'I extending upwardly from the torsion structure i'I. The hub 48, to which the spoke elements 46 and 47 are secured, is soldered between the spaced upper ends of the prongs.

The second lateral support 44 is similar in construction to support 43 and comprises a rim 4B also rigidly secured to the housing sidewalls 22, A plurality of spokes 49 and 50 are secured near the bottom portion of torsion structure Il as close to axis YY as possible and extend radially outward therefrom and are secured in rim 48. This structure permits relative twisting between torsion structure I'I and sidewalls 22 but at the same time will prevent translational or rocking movements therebetween. As above described, these lateral supports about the axis YY space the lateral vibration resonances, tuning them to frequencies which greatly minimize spurious rocking components of vibration due to external vibrations, or drive unbalance, or mass unbalance in the tines, and hence decrease their effect on the torsion pick-ods. Lateral supports 43 and 44 also provide a rugged support for the apparatus when the same is subjected to severe shocks.

Thus, the lateral supports 43 and 44 together with the torsion spring I8 form a composite torsion spring, spokes 46, il? and 49, 5@ being stii to lateral translation and the tube or torsion spring i8 being stiff to axial translation. Oi course, the composite torsion structure is tuned so that the torsion resonance coincides with the tuning fork natural frequency, whereas the translational resonances do not. It may be desirable, in some applications, and for manufacturing conveniences,

to support the entire tuning fork assembly by the lateral supports 43 and 44 alone, eliminating entirely the torsion spring or axial support I8.

Even with the above construction, rocking components of vibration may reach the torsion pickois, but they are of very low order and may be substantially compensated for by providing an adjustment of the pick-oil coils 33', 34, 35 and 36 relative to the pick-oir armatures 32 and 33, to be hereinafter more fully described.

In order to drive the tines as near as possible in their natural plane of vibration without coercion, we have provided means for adjusting the electromagnetic drive means 20 and 2I. For this purpose we have supported drive coil members 55, 5S in a cylindrical supporting member 5l (see Figs. 2, 3 and 4) which is provided with a central opening 58 adapted to receive the ends of tines I4 and I5, Capacity pickup 23 is positioned in opening 58 so that it lies between the open ends (lil of the tines and is insulated from supporting member 57 by a suitable insulating piece 59. The whole supporting member 57 is adjustable as a unit in directions both laterally and rotationally relative to the axis YY.

To provide for the adjustment of drive coils 55 and 5S in lateral directions relative to axis YY, we have milled or otherwise formed vertical slots G, SI, 52 and 63 in supporting member 5T, which extend upwardly from the bottom thereof to a position approximately one-half the width thereof. These slots are positioned relatively close to the outside edge of cylindrical support 57 and form chordal segments or outer portions El thereof, the outer periphery of which will bear against the wall 22 of the housing. Through the vertical length of each of the slots te, 6i, 52 and 63 and preferably on the axes XX and respectively, we have drilled a tapered hole 64 into which a conical-ended screw b5 is inserted. A tapped hole B6 provides for moving the conical-ended screw along the length of the tapered hole Sil. Thus it will be seen that as the conical-ended screw 55 is raised or lowered in the tapered hole E4, the chordal segment @i of support member 51 is forced against the housing wall 22. Segment El of supporting member is rendered relatively iiexible by milling or cutting suitable lateral slots 6l therein to reduce the thickness of the material between member 5l and chordal segment B7. Four of these screw and slot arrangements are provided, two for adjusting the drive coils along the XX axis and two for adjusting the coils along the ZZ axis. Therefore, by tightening one screw, say screw 85, and loosening corresponding screw 65', the support member 5'! and drive coils 55 and 58 will be moved as a unit along the axis XX. The exact same arrangement is provided for moving support member 51 along axis ZZ', as by screw 68, SS in Fig. 3. It will be noted that the adjustments described above may conveniently be made from the end of the housing.

Rotational adjustment of the drive coils 55 and 56 about the axis YY is provided by a similar arrangement. For this purpose we have milled out o-r cut away the supporting member 5l' as at 'I0 and lI to provide suitable bearing surfaces 72, 73. A slotted adjusting member l is formed integrally with or suitably secured to the housing wall 22 (see Figs. 4 and 6) and has drilled along the length of the slot thereof a tapered hole i5. As above, into this hole is tted a conical-ended screw 'I5 which bears against the tapered walls of the hole 15. The slot in member Tai is so positioned that raising or lowering of screw 'It will cause lower portion 'I'I of member i4 to be forced against the bearing surfaces 13. A similar member 14 is provided adjacent the `bearing surface 'I2 and raising or lowering of scr-ew 7S will cause lower portion II 'to bear against the bearing surface '12. The slotted adjusting members 74, are provided with suitable lateral slots Il for reducing the thickness of the material between member 14, '14 and the lower portion l?, 'i'E" thereof to thereby provide reasonable flexibility in lower portions ll, 'I1'. It will be not-ed that adjusting members '14, T4 are placed on oppo site sides of axis XX so that by raising one screw and lowering the other screw the supporting member 5! may be rotated about axis YY. This adjustment is also made from the top of the apparatus.

Even after careful adjustment of the drive coils 55, 56 and the provision of the lateral supports and isolation means, .spurious vibrations may still reach the pick-ois 30 vand 3l and affect the rate oi turn signal, Spurious lateral vibrations may be eiiectively cancelled by adjusting the position of the pick-oir coils 33, 34, 35 and 36 relative to the vanes 32 and 33. This adjustment is accomplished in a similar manner as the adjustment of drive coils 55, 55. Since the adjustment of the pairs of drive coils 33 and 313, and 35 and 3S are identical, only the adjusting structure of one set, 35 and 35, will be described in detail, reference being made particularly to Figs, 5 and 7. The vanes 32 and 33 preferably extend radially from a hexagonal or suitably shaped member i lil having a bore extending centrally therethrough and a peripheral recess in the side walls of said bore at the lower end thereof forming a shoulder. The upper end of the bore is adapted to receive the lower end of member .il while the rlanged upper end of the cylindrical torsion spring E8 is adapted to fit within the bore of member ii@ and within the peripheral recess at the lower end thereof. Both the member il' and the flanged upper end of torsion spring i8 are securely anixed to the member ri as, for example, by means ci bracing or welding. Secured to base I9 is a support se having upstanding portions di, t2 on which are mounted pick-oir" coils 35 and 3E. Support s@ is positioned on base member E S so that upstanding portions 3i and 82 thereof and coils Se and B lie closely adjacent to opposite faces of the vane 33. For providing movement of coils e and i towards and away from the opposite faces ci the vane 33, we have provided a, plurality of slots Es, Sii and 86. These slots 33 and in support Et extend from opposite sides or" upstanding portions Si and at an angle towards each other to form a relatively resilient coupling 3l between ups'tanding portion 8.! and the support Sil. Similarly, slots 35 and S5 Vextend downwardly from each side of lupstanding portion 82 at an angie towards each other, so that a relatively resilient coupling te is provided between upstanding portion 32 and the support 2S. Tapered holes 52E, 9i, $2 and S3 are drilled substantially along the length of slots 83, 816, B5 and 3S, respectively, and conical-ended screws 9&1, 95, yBES and Sl are inserted in the respective tapered holes. rEhus, to move coils 35, for example, towards the face cf the vane 33, screw S4 may be raised in tapered hole 90 and simultaneously screw 95 be lowered inthe corresponding tapered hole si thus forcing ups'tanding portion Si and associated coils 35 to pivot about the resilient coupling Coils i5 may be similarly adjusted relative to the eppost face of vane 33 through respectively raising vand lowering of Screws 3S and Sil'. As in the case of the tine drive assembly adjustment, the torsion pickup coils may be similarly adjusted from the ends oi the apparatus so that the supporting structure and the entire sensitive apparatus is not disturbed. t is also important to note that the adjustments are entirely within either the tine drive assembly or the torsion pick-off assembly and in no way affect any or" the other elementsof the apparatus.

It is important, that upon completion or termination of an applied rate of turn, torsional vibration caused thereby should be brought to a in as short a time as possible and at a predetermined rate. For this purpose we have provided a damping means which, in the embodiment illustrated, comprises a metal core 63 secured to base `i9 oi such a size that it will substantially completely fill the cylindrical opening formed by the -cylindrical torsion spring I8, leaving only a very thin space between the walls of core it@ and the inside .periphery of spring it. Positioned at the top of core i is a plurality of radially extending rods lili which extend into holes m2 in the lower portion of the torsion structure il. The clearance between these rods and holes is extremely small, say, for example, or" the order or" rive thousandths of an inch. This small space, and the space -between core it and spring iii, is lled with `a suitable viscous iluid, such as, for example, a low viscosity Silicone oil. See particularly Figs. 2, 3 and 5. Thus, in the presence of a torsional vibration the Silicone fluid surrounding 'the rods il is squeezed or forced with turbulence about the walls of the holes iii. Such a construction provides adequate damping oigthe torsional vibration to make it decay at an appropriate rate upon termination of an applied rate of turn.

l/Vhile we have described our invention in its preferred embodiment, it is to be understood that the words which we have used are words or" description rather than of limitation and that changes within the purview oi the appended claims may be made without departing from the rue scope and spirit of our invention in. its broader aspects.

What is claimed is:

1. Apparatus for measuring the angular rate or" turn or a craft about an axis comprising a housing having substantially rigid side walls a base, a tuning fork having a heel portion and a pair of tines integral therewith and mounted within said housing to vibrate in a plane including said axis, a rst vibration-damping supporting means for said fork comprising a som-what elongated mass to one end of which the supporting means adjacent its other end detecting torsional vibrations thereof providing a signal output proportional thereto, and laterally extending second supporting me for said first supporting means connected to s i rst supporting means and the housing side wails.

2. In al device for measuring turning ino-vements of a craft about an axis, a tuning ieri: mounted to vibrate in a pla-ne including axis and having a heel por-tion and a pair of integral therewith, the vibration of said in said plane producing a torsional vibration about said axis upon turning movements thereof about said axis, a base member, and an intermediate portion connecting said fork with said 1oase ber, means forming a nodal coupling between said heel portion and said intermediate portion, a torsion spring resilientiy coupling said ir mediate portion with said base member for p oviding relative torsional movement between said base member and said fork, means for isolating said torsion spring from vibratory stresses paralleling said axis due to deformation stresses in the tuning fork heel portion resulting said tine vibration and transmitted to said intermediate portion by said nodal coupling, said isolati means comprising a pair of slots extending inwardly from opposite sides or" said intermediate portion to denne a substantially narrow, elongated connecting web extending rically across said intermediate portion, and lying in a -plane including said axis.

3. In a device for measuring turning movements of a craft about an axis, a tuning fork mounted to vibrate in a plane including said axis and having a heel portion and a pair of tines integral therewith, the vibration of said tines in said plane producing a torsional vibration about said axis upon turning movements thereof about said axis, a base member, and an intermediate portion connecting said forli with said base me; ber, means forming a nodal coupling between said heel portion and said intermediate portion, a torsion spring i'esiliently coupling said intermediate portion witlA said base member for pron viding relative torsional movement between said base member and said fork means for isolating said torsion spring from vibratory stresses par alleling said axis due to deformation stresses in the tuning fork heel portion resulting from said` tine vibration and transmitted to said intermedin ate portion by said nodal coupling, said isolating means comprising a nrst pair of slots extending inwardly from opposite sides of said intermediate portion to denne a rst substantially narrow, elongated connecting webI extending diametrically across said intermediate portion, and a second pair of slots also extending inwardly from opposite sides of said intermediate portion to dene a second, substantially narrow, elongated connecting web extending diametrically across said intermediate portion, said webs being angularly disposed relative to each other in said intermediate portion.

ll. In a device for measuring the rate of turning movements or" a craft about an axis, a .tuning fork mounted to vibrate in a plane including said axis and having a heel portion and a pair of tines integral therewith, the vibration of said tines in said plane producing a torsional vibration about said axis upon .turning movements thereof about said axis, a base member, an intermediate portion connecting said fork with said base member, means forming a nodal coupling between said heel portion and said intermediate portion, a torsion spring resiliently coupling said intermediate portion with said base member for providing relative torsional movement between said base member and said fork, means for isolating said torsion spring from vibratory stresses paralleling said axis due to deformation stresses in the tuning fork heel portion resulting from said tine vibration and transmitted to said intermediate portion by said nodal coupling, said isolating means comprising, a rst pair of slots extending inwardly from opposite sides of said intermediate portion to define a first substantially, narrow, elongated connecting web extending diametrically across said intermediate portion in a plan-e substantially parallel to the plane of vibration of said tines, and a second pair of slots also extending inwardly from opposite sides of said intermediate portion to denne a second substantially narrow, elongated `connecting web -extending diametrically across said intermediate portion in a plane substantially at right angles to the plane of vibration of sai .tines 5. in a device for measuring the rate of turning movements of a craft about an axis, a tuning fork mounted to vibrate in a plane including said axis and having a heel portion and a pair of tines integral therewith, the Vibration or" said tines in said plane producing a torsional vibration about said axis proportional to the magnitude and direction of turning movements thereof about said axis, a base member, and an intermediate portion connecting said fori; with said base, means forming a nodal coupling between said heel portion and said intermediate portion, a torsion spring resiliently coupling said intermediate portion With said base member for providing relative torsional movement between said base member and said fork, means for isolating said torsion spring from vibrations par llel to Said axis due to deformation stresses in the tuning forli heel portion resulting fr in said tine vibration and transmitted to said intermediate portion by said nodal coupling, said o'ating means comprising a iirst pair of slots ending -Tardly from opposite sides of -dei sediu ate portion in a plane normal to to denne a first substantially narrow, elongated connecting web extending diametrically across int rmediate portion in a plane parallel to the plane of vibration of said tines, a second pair of slots also extending inwardly from opposite sides of said intermediate portion in a plane nor al to said axis to denne a second substannarrow, elongated connecting web extending across said intermediate portion in a plane at right angles to the plane of vibration ci said tines.

5. Apparatus responsive to the rate of turn of a craft about an axis, a housing having substantially rigid sidewalls and a base, a tuning fori. having a heel portion and a pair or tines integral 'therewith and mounted to vibrate in a plane including said axis, a vibration-damping mass to which the heel of said fork is secured, resilient torsional constraining means connecting mass to said case while permitting angular positional variations about said axis between forli and said base, said fork and being capable of vibrations laterally of said axis generated by unsymmetrically balanced masses in tines, means responsive to the angular posi tional variations of said mass for detecting rotation of said base, and a. plurality of laterally extending coupling rods connected to mass and to said housing sidewalls for altering the natural frequency of said lateral vibrations to frequencies dii-ferent from the frequency of vibration of said tines, whereby said detecting means will be substantially unaffected by lateral vibrations oi frequencies in the region oi"- said tine frequency.

7. Apparatus responsive to the rate of turn of craft about an axis, a housing having substantially rigid sidewalls and a base, a tuning fori; having a heel portion and a pair of tines integral therewith and mounted in said housinGv means including a reference current source for driving the tines thereof alternately, rapidly, and continuously toward each other and away from each other in a plane including said axis and at a frequency corresponding to the natural 'reruency of vibration of said fork and said reicrence current source whereby a torsional vibration about said axis proportional to the direction and magnitude of turning movemeA s craft about said axis is generated, a ibration-damping mass to which the heel of fork is secured, a resilient connection connecting said mass with said base member to permit torsional vibration or said mass, vibration-responsive nal generating means coupled with said resilient connection and said base adapted to provide an output signal depending upon the amplitude and phase sense of said torsional Vibration relative to the phase of said reference current source, laterally-extending coupling means betwee said intermediate portion and said housing sidewalls for isolating said signal generating means from lateral vibrations of said fork and intermediate portion produced by externally caused lateral vibrations of said housing, whereby output 11 signal will be unaffected by said external vibrations.

8. Apparatus responsive to the rate of turn of a craft about an axis, a housing having substantially rigid sidewalls and a base, a tuning fork having a heel portion and a pair of tines integral therewith and mounted in said housing means including a reference current source for driving the tines thereof alternately, rapidly, and continuously toward each other and away from each other' in a plane including said axis at a frequency' of vibration corresponding to the natural frequency of vibration of said fork and said reference current source, whereby a torsional vibration about said axis proportional to the direction and'rnagnitude of turning movements of the craft about said axis is generated, a torsion spring having one end thereof secured to said base member, an intermediate vibration-damping portion comprising a mass connected at one end to the heel` of said fork and at the other end to said torsion spring, said torsion spring and intermediate coupling being capable of reed-like vibrations laterally of said axis having a node in the region of said torsion spring, means for altering the natural frequency of said reed-like vibrations in the region of said tine frequency to frequencies different from the said tine frequency, a pair of lateral supports, one at the lower end of said intermediate portion and in the region of an antinode of one mode of said reedlilie vibration and the other at the upper end thereof in the region of an antinode of another mode of said reed-like vibration, each of said supports comprising a plurality of angularlydisposed, rod-like elements each having one end thereof fixed on said intermediate portion and the other end thereof extending radially outwardly from said intermediate portion and secured in said rigid sidewalls, whereby said fork and intermediate portion are resiliently supported in torsion about said axis but are substantially rigidly supported against lateral movements thereof relative to said axis.

9. In a device for measuring the rate of turning movements of a craft about an axis, a housing, a vsupport tted within said housing to engage opposite sides thereof, a tuning fora having a pair of rcsiliently connected tines mounted for vibration in a plane including said axis, drive means secured to said support for vibrating said tines alternately towards each other and away from each other, slots in opposite sides of said support in part separating the centralA portion thereof from the housing-engaging peripheral portions, and screw threaded wedges paralleling said axis and disposed respectively in the zones f said slots for urging the portions of said support apart, whereby said drive means may be adusted to produce driving forces on said tines providing vibration thereof in a substantially purely planar manner.

le. in a device for measuring the rate of turning movements of a craft about an axis, a housing, a support fitted within said housing to engage opposite sides thereof, a tuning forkihaving a pair of resiliently connected tines mounted for vibration in plane including said axis, drive means secured to said support for vibrating said tines alternately towards each other and away from each other, said support having spaced surfaces extending inwardly from the periphery thereof, bosses extending from said housing into engagement respectively with said surfaces, said bosses being slotted in a direction generally paralleling saidsurfaces, and screw threaded wedges paralleling said axis and disposed in the zones of the slots of said bosses, said bosses being so constructed and arranged as to urge said` support in a rotational manner about said axis in either direction when said wedges are operated, whereby said drive means be adjusted to produce driving forces on said tines provi ling vibration thereof in a substantially purely planar manner.

11. In a device for measuring the rate of tur ing movements of a craft about an axis, a housing having substantially rigid sidewalls, a tuning forli having a pair of resiliently connected tines mounted for vibration in a plane including said axis, a support member tted within said housing to engage opposite sidewalls thereof and adjacent the open ends of said fork, electromagnetic drive means for vibrating said tines alternately towards each other and away from each other fixedly mounted on said support member, slots in opposite sides of said support member and extending in substantially mutually perpendicular relation to separate in part the central portion of said support member from the housing engaging peripheral portions thereof, a tapered opening passing through said support inember and communicating with each slot, and screw threaded wedges disposed within tapered openings for urging the portions of said support member apart, whereby said drive means may be adjusted to produce driving forces on said tines providing vibration thereof in a purely planar manner.

l2. A device for detecting the rate of turning movements of a craft about an xis, a base meinber, a tuning fori; having elastically interconnected tines, means including a reference current source for driving the tines alternately, rapidly, and continuously towards each other away from each other in a plane including axis whereby a torsional vibration about said axis proportional to the direction and magnitude of turning movements of said craft is generate a torsion member having one end thereof fixed to said base member and the other end iixed to said fork, said torsion member resiliently coupling said fori: with said base member for providing relative torsional movement therebetween, vibration-responsive means for detecting the magnitude and direction of said torsional vibration dependent upon the amplitude and phase of said torsional vibration relative to the phase of said reference current source, said last-mentioned means including a pick-od comprising a vane fixed to said torsion member for torsional movement therewith and a plurality of magnetic coils on both sides of said vane and adjstably secured to said base, and means for adjusting the spaeings of said magnetic coils relative to said vane, whereby to compensate for spurious torsional vibrations which may be generated by spurious vibrations of said tines.

13. A device for detecting the rate of turning movements of a craft about an axis, a base merober, a tuning fork having elastically interconnected tines, means including a reference current source for driving said tines, alternately, rapidly, and continuously towards each other and away from each other in a plane including said axis whereby a torsional vibration about said axis proportional to the direction and magnitude of turning movements of said craft is generated, a torsion member having one end thereof xed to said base memberV and the other end thereof fixed to said fork, said torsion spring resiliently coupling said forli and said base for providing relative torsional movements therebetween, electro magnetic pick-olf means for detecting the magnitude and direction of said torsional vibration de pendent upon the amplitude and phase of said torsional vibration relative to the phase of said reference current source, said pick-oil' means comprising an armature member mounted on said torsion member and a held member comprising a plurality of magnetic coils adjustably mounted on said base member adjacent and to both sides of said armature member, and means for separately adjusting the spacings of said magnetic coils relative to said armature member, whereby to be rendered unresponsive to spurious vibrations which may be generated by spurious vibrations of said tines.

le. A device for detecting the rate of turning movements of a craft about an axis, a base member, a turning fork having elastically interconnected tines., means including a reference cur` rent source for driving said tines alternately, rapidly, and continuously towards each other and away from each other in a plane including said axis whereby a torsional vibration about said axis proportional to the direction and magnitude of turning movements of said craft is generated, a torsion spring having one end thereof fixed to said base member, an intermediate portion connecting said fork with the other end of said torsion spring, said torsion spring resiliently coupling fork and intermediate portion with said base member' for providing relative torsional movement therebetween, electromagnetic picko means for detecting the magnitude and direction of said torsional vibration dependent upon the amplitude and phase of said torsional vibration relative to the phase of said reference current source, said last-mentioned means comprising a pair of vanes secured to said intermedin ate portion for torsional movement therewith, said vanes extending outwardly on opposite sides of said intermediate portion in a common plane including said axis and forming the armatures of said electromagnetic pick-offs, and irst and second pairs of field members respectively positioned closely adjacent opposite faces of each of said vanes and secured to said base member, said field members being so electrically interconnected that signals generated therein will be additive upon torsional movements of said vanes about said axis but will cancel upon translational movements thereof, and means for separately adjusting the spacings or the field members on opposite sides of one of said vanes whereby to render said pickoff substantially unresponsive to spurious vibrations.

l5. A device for detecting the rate of turning movements of a craft about an axis, a base member, a tuning iork having elastically interconnected tines, means including a reference current source for driving said tines alternately, rapidly, and continuously towards each other and away from each other in a plane including said axis whereby a torsional vibration about said axis proportional to the direction and magnitude of turning movements of said craft is generated, a torsion spring having one end thereof fixed to said base member, an intermediate portion connecting said fork with the other end or said torsion spring', said torsion spring resiliently coupling said fork and intermediate portion with said base member for providing relative torsional movement therebetween, electromagnetic pick-off means for detecting the magnitude and direction of said torsional vibration dependent upon the amplitude and phase of said torsional vibration relative to the phase of said reference current source, said last-mentioned means comprising a pair of vanes secured to said intermediate portion for torsional movement therewith, said vanes extending outwardly on opposite sides of said intermediate portion in a common plane including said axis and forming the armatures of said electromagnetic pick-ons, iirst and second pairs of field members respectively positioned closely adjacent opposite faces of each of said vanes and adjustably secured to said base member, the eld members lying adjacent diametrically opposite faces of said vanes being electrically interconnected, whereby the signals generated therein will be additive with torsional movement of said vanes about said axis but will cancel upon translational movements thereof, and means for individually adjusting said pairs of eld members relative to said vanes in directions substantially perpendicular to the faces of said vanes, whereby said pickup means may be adjusted to be unresponsive to spurious vibrations which may be generated by spurious vibrations of said tines.

l5. Apparatus responsive to the rate of turn of a craft about an axis, a housing having substantially rigid sidewalls, a tuning fork mounted to vibrate in a plane including said axis, resilient torsional constraining means connecting said fork to said housing for permitting angular positional variations about said axis between said fork and said housing according to variations of torsion in said resilient means, said last-mentioned means comprising a plurality of angularly disposed, rodM like elements each having one end thereof afiixed to said constraining means in a central zone thereof but otherwise passing freely therethrough and the other end thereof extending radially outu wardly from said constraining means and being secured in said rigid sidewalls, whereby said forli assembly is resiliently supported in torsion about said axis but is substantially rigidly supported against lateral movements thereof relative to said axis.

17. Apparatus responsive to the rate of turn of a craft about an axis, a tuning fork mounted to vibrate in a plane including said axis, resilient torsional constraining means connecting said fork to said base for permitting relative angular positional variations about said axis between said fork and said base according to variations or" torsion in said resilient connecting means, said fori: and resilient constraining means being capable or" spurious torsional vibrations about said axis generated by unsymmetrically balanced masses in said tines, said resilient torsional constraining means comprising a tubular member connected at one end with said fork and at the other end to said base and having such dirnenm sions that any spurious resonances excited therein by said spurious vibrations are different from the resonant frequency of torsional vibration produced by rotation of said base relative to said tuning fork.

18. Apparatus responsive to the rate of turn of a craft about an axis, a base member, a tuning fork mounted to vibrate in a plane including said axis, a substantially thin tubular member connected with said fork and to said base member for permitting angular positional variations about said axis between said fork and said base member according to variations of torsion in said tubular member, said tubular member being provided with a recess ina side wall thereof, damping means ybetween said base member and said mb-ular member comprising a rod having one end 'thereof fixed to said base member and extending Within said recess in said tubular member, the dimensions of said tubular member and rod being such as to define a substantially thin space between the Walls of the recess in said tubular member and said rod. surface, and a viscous fluid iiing said space having high viscosity such that torsional vibrations produced by turning movements o1 said craft about said axis may be reduced to zero at a predetermined rate upon termination of said turning movements.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,309,853 Lyman et a1 Feb. 2, 1943 2,385,005 Langer Sept. 18, 1945 2,440,605 Hathaway Apr. 27, 1948 2,455,939 Meredith Dec. 14, 1948 2,513,340 Lyman July 4, 1950 

